Devices for recovering of oil and gas from long, horizontal and vertical wells are known from U.S. Pat. Nos. 4,821,801, 4,858,691, 4,577,691 and GB patent publication No. 2169018. These known devices comprise a perforated drainage pipe with, for example, a filter for control of sand around the pipe. A considerable disadvantage with the known devices for oil/and or gas production in highly permeable geological formations is that the pressure in the drainage pipe increases exponentially in the upstream direction as a result of the flow friction in the pipe. Because the differential pressure between the reservoir and the drainage pipe will decrease upstream as a result, the quantity of oil and/or gas flowing from the reservoir into the drainage pipe will decrease correspondingly. The total oil and/or gas produced by this means will therefore be low. With thin oil zones and highly permeable geological formations, there is further a high risk that of coning, i. e. flow of unwanted water or gas into the drainage pipe downstream, where the velocity of the oil flow from the reservoir to the pipe is the greatest.
When extracting oil from reservoirs by injection of steam or using combustion, the differential pressure can vary along the drainage pipe. This may cause problems should injected steam or combustion gas reach the valves used for draining fluid from the reservoir into the production pipe, as many such valves are not able to close to prevent steam or combustion gas from entering the production pipe. In particular, if the differential pressure is relatively low, ingress of steam or combustion gas can lead to a “short circuit” of the injection pressure and the production pressure. This will cause the differential pressure to drop even further, which has a negative effect on the efficiency of the drainage process (injected energy vs. produced oil volume).
A further result of areas with low pressure differential combined with high temperature, or hot spots, is that fluid with low viscosity from high temperature regions of the reservoir will dominate the inflow into the production pipe. In this way, the production pipe will have an undesirable inflow profile along its length.
From World Oil, vol. 212, N. 11 (November 1991), pages 73-80, is previously known to divide a drainage pipe into sections with one or more inflow restriction devices such as sliding sleeves or throttling devices. However, this reference is mainly dealing with the use of inflow control to limit the inflow rate for up hole zones and thereby avoid or reduce coning of water and or gas.
WO-A-9208875 describes a horizontal production pipe comprising a plurality of production sections connected by mixing chambers having a larger internal diameter than the production sections. The production sections comprise an external slotted liner which can be considered as performing a filtering action. However, the sequence of sections of different diameter creates flow turbulence and prevents the running of work-over tools operated along the outer surface of the production pipe.
Devices as disclosed in WO2009/088292 and WO 2008/004875 are robust, can withstand large forces and high temperatures, can prevent draw downs (variations in differential pressure), need no energy supply, can withstand sand production, yet are reliable, simple and very cheap. However, several improvements might nevertheless be made to increase the performance and longevity of the above device in which many of the different embodiments of WO2009/088292 and WO 2008/004875 describe a disc as the movable body of the valve.
When extracting oil and or gas from geological production formations, fluids of different qualities, i.e. oil, gas, water (and sand) is produced in different amounts and mixtures depending on the property or quality of the formation. None of the above-mentioned, known devices are able to distinguish between and control the inflow of oil, gas or water on the basis of their relative composition and/or quality. In particular, the known devices are not able to perform a satisfactory control of variations in inflow into the production pipe due to variations of differential pressure caused by temperature variations. WO 2008/004875 does disclose a temperature responsive valve, but the suggested solution involves bending the movable valve body by means of a bi-metallic element. The suggested solution is relatively complex and requires an expensive valve body that is susceptible to wear caused by repetitive deformation. WO 2005/103443 discloses a temperature responsive valve where the material of a valve body has a linear expansion coefficient that is greater than that of the well pipe material. When the temperature increases, the valve body expands more than the well pipe and moves in the direction of its closed position covering the opening. This solution will give a relatively long response time, causing large quantities of gas and/or hot liquid to enter the drainage pipe to disturb the flow through the drainage pipe.
The present invention provides an improved valve arrangement which aims to minimize problems relating to variations in inflow into the production pipe due to temperature variations.